Its unlike traditional footsies. You aren't really jockying for good position or pokes, you are constantly throwing out light damage and knockback while waiting to see what they do. For example, I like to do landing pellets until they are conditioned to shield when I land. Then I do empty land into dashgrab, pummel em once, then chuck them back out, or up if they are a character that is vulnerable above me. With some characters, such as luigi, simply pelting with lemons at midrange is strong enough to win the matches (Obviously you need other things, but its a solid gameplan).
So, his footsies are not quite normal footsies, but they are very strong. How strong? MU dependent. Characters with strong zone breakers tend to not have problems outfootsying mega, though this of course player to player (you can predict the zone breaker and push them out, its what wins matches for mega!). He is heavy so you can afford to make some mistakes, as long as you don't die for the mistake as often as you are getting kills of course. Im getting off topic, back to footsies:
Burst movement isn't always good enough to zonebreak megaman anyways. For example, Monkey Kick gets slowed by lemons enough to reactively punish after they sift through the lemon. It stops bayo's grounded side B cold. It can even stop bouncing fish, though this has to hit just right for it to occur.
The only case where megaman really really just gets demolished in footsies is shiek, as she is more mobile, gets confirms for days since mega is heavy, and needles win any projectile war for some dumb, dumb reason.
Another really cool footsy type trick is how you can pivot an Ftilt from a run: This means megaman can full speed run away then immediately be walking the opposite direction firing lemons. Great spacing manuever.
Does this help with your question?